1. Field of the Invention
This invention relates generally to hot-gas cleanup systems and more particularly to a gasket assembly that provides a particulate barrier seal between the body of a candle filter element and the filter holder.
2. Background Information
Modern industrial methods have resulted in a need for an apparatus that is capable of efficiently filtering high temperature combustion gases containing particulate material. In combustion turbine applications, for example, a combustion turbine uses energy generated from hot pressurized combustion gases produced by burning natural or propane gas, petroleum distillates or low ash fuel oil. When coal and other solid fuels are burned, particulates carried over from the combustion of such solid fuels can cause turbine blade erosion and fouling. An efficient system for filtering of such hot combustion gases would permit the use of such solid fuels. As another example, in conventional boiler operations, the boilers undergo routine shutdown for cleaning the fireside surfaces and for inspection. An efficient hot gas filtering system would greatly extend the life and operational time for a boiler to operate between inspections. Fouling of the fireside surface due to ash deposition and corrosion would be eliminated or minimized.
U.S. Pat. No. 5,185,019 discloses a thick walled hot gas candle filter mounting assembly. U.S. Pat. No. 5,474,586 discloses a thin walled hot gas candle filter mounting assembly, and discusses gasket assemblies generally, providing little information as to their construction.
Additionally, U.S. Ser. No. 08/636,432, filed on Apr. 23, 1996 (Alvin et al.), attempted to provide a filtering apparatus that can filter high temperature, high pressure, aggressive gases, having an improved, easily mounted double gasket assembly that can be employed with a conventional candle filter and a thin walled composite. There, both the topmost and bottom gaskets consisted of a two component system, made of an interior ceramic fibrous mat filler in compliant annular form covered by a short sheet of a woven or braided sleeving surrounding or encasing the mat filler, which sleeving was stitched together on the outside diameter of the gasket.
Operational experiences show that the prior two component gaskets were subject to fraying and loss of the central mat filler. This could leave, in the case of the top gasket, a void between the metal retainer ring and the top of the porous ceramic and/or metal candle filter, whereby racheting of the candle filter within the housing may cause failure of the candle filter and/or passage of particulate fines into the clean gas stream. This two component system also requires specialty cutting of the interior mat to tolerance specifications. The plurality of gaskets were employed to provide cushioning and sealing around a filter element to prevent particulate matter from passing between the filter body and its associated metal housing. A cast nut was provided as a coupling means to secure the assembled housing, filter element and gaskets.
In view of the above problems, what is needed is a different type of gasket assembly which is less expensive and less complicated to manufacture, which will be less likely to separate, and which if it does start to separate will retain the spacing and seal between metal retainer ring, metal housing, and the ceramic and/or porous metal candle filter.